1. Field of the Invention
The present invention relates to auxiliary powered units for assisting vehicles in moving load trailers. In particular, the present invention relates to an apparatus for controlling the speed of the powered trailer dependent on the position and motion of the vehicle relative to the powered trailer.
2. Description of the Prior Art
Increased concerns about efficient energy consumption have led to the production of smaller and lighter automobiles. Such vehicles attain greater fuel efficiencies than previous models by having smaller engines, smaller bodies and many components made of lightweight materials. Because these lighter vehicles have smaller engines, their ability to pull trailers of any substantial load is greatly diminished. In addition, because such vehicles are so lightweight, substantial stress is created on a vehicle's frame when a heavy trailer is hitched thereto. Therefore, when a trailer of substantial load is to be moved by a small automobile, a booster source of power with means for preventing the weight of the trailer from being transferred completely onto the automobile frame is desired.
One approach for providing an supplemental source of power to pull a trailer is to place a booster engine on the trailer itself. This concept is shown in U.S. Pat. No. 2,630,871, granted to Simpkins on Mar. 10, 1953 and U.S. Pat. No. 4,185,710, granted to Kronogard on Jan. 29, 1980. The devices of these patents do not overcome the problem of stress caused by excess tongue weight on the vehicle frame. They do provide a booster motor to aid in pulling the trailer, but the devices of these patents increase rather than lighten the trailer weight placed on the vehicle.
A more satisfactory method for assisting a vehicle in pulling a heavy load trailer is to provide an auxiliary booster trailer between the vehicle and the load trailer. This concept is shown in U.S. Pat. No. 2,153,468, granted to Heyn on Apr. 4, 1939 and U.S. Pat. No. 3,695,373, granted to Bostrom on Oct. 3, 1972. The Heyn Patent shows a powered booster trailer to provide more pulling power and aid in distributing the weight of the load between the various axles of the vehicle, booster trailer and load trailer. No details are provided as to how the motor on the Heyn trailer is controlled or coordinated with the motor on the vehicle. The Bostrum device discloses an auxiliary trailer with a booster motor, but is mainly concerned with a mechanism for changing the gears in a manned drive unit and the auxiliary trailer simultaneously. This mechanism is a complex hydraulic connection system between the drive unit and auxiliary trailer gears so that the auxiliary trailer gears are controlled in dependence upon the drive unit gears.
None of these prior art patents discloses an auxiliary powered trailer wherein the powered trailer is provided with a tongue assembly between it and the vehicle which substantially eliminates the transfer of load weight from the powered trailer and load trailer to the powered vehicle or which is suitable for use with small automobiles. The control means disclosed in these patents for controlling the operation of the engines on the powered trailers are somewhat complicated and generally operably connected to the engine or transmission of the powered vehicle. In addition, the safety problems inherent in having a driverless powered vehicle on the highway is not addressed by any of the prior devices.